Eight- and 16-membered cyanuric-sulfanuric ring systems: C2N4S2-->C2N3S ring contraction

Polymeric materials based on main group elements: the recent development of ambient temperature and controlled routes to polyphosphazenes

This Perspective discusses the development of new routes to polyphosphazenes, [R(2)P[double bond, length as m-dash]N](n), that occur at ambient temperature and, in some cases, allow molecular weight control and access to narrow molecular weight distributions and block copolymers. For example, the room temperature silyl-carborane initiated ring-opening polymerisation of (NPCl(2))(3) is described together with chain growth condensation polymerisations of phosphoranimines Cl(3)P[double bond, length as m-dash]NSiMe(3) and BrMePhP[double bond, length as m-dash]NSiMe(3). Recent works on donor-stabilised cationic phosphoranimines are also discussed.

Synthesis and properties of Ph2S(=N-(Ph2)S[triple bond]N)2

A new type of lambda6-sulfanenitrile with an SN triple bond at both ends, Ph2S(=N-(Ph2)S[triple bond]N)2 (5), was prepared in excellent yield from the one-pot synthesis of diphenylsulfimide (Ph2SNH) with fluoro(diphenyl)-lambda6-sulfanenitrile (Ph2FSN) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene. Its molecular structure was determined by X-ray crystallographic analysis. Compound 5 reacted further with methyl triflate and trifluoromethanesulfonic anhydride to afford the corresponding bis-N-methylated and -N-sulfonated compounds.

A New, Convenient Synthesis of the Linear Phosphazene Salt [Cl3PNPCl3]Cl: Preparation of Higher Linear Homologues [Cl3PN−(PCl2N)xPCl3]Cl (x = 1−3) and the 16-Membered Macrocycle [NCCl(NPCl2)3]2

An improved synthetic route to the linear phosphazene salt [Cl3P=N=PCl3]Cl is reported. This species is a useful precursor to higher linear homologues and also to heterocycles such as the 16-membered carbophosphazene macrocycle [NCCl(NPCl2)3]2.

Structural studies of dithiatetrazocines: X-ray crystal structures of the symmetric dithiatetrazocines p-XC6H4CN4S2CC6H4X [X = NO2, Br] and the first unsymmetric dithiatetrazocine, p-BrC6H4CN4S2CC6H4NO2

Oxidation of equimolar amounts of [p-BrC6H4CNSSN]Cl and [p-O2NC6H4CNSSN]Cl with elemental O2 in the presence of Ph3Sb in MeCN yields a mixture of the symmetric dithiatetrazocines, O2NC6H4CN4S2CC6H4NO2 (1) and BrC6H4CN4S2CC6H4Br (2) as well as the unsymmetrically substituted derivative BrC6H4CN4S2CC6H4NO2 (3). The structures of compounds 1–3 are determined by X-ray diffraction: 1 crystallizes in the monoclinic space group P21/c (a = 8.6397(4), b = 5.8359(4), c = 14.9767(11) Å, β = 92.088(4)°) with half a molecule in the asymmetric unit; 2 crystallizes in the triclinic space group P[Formula: see text] (a = 6.5330(5), b = 8.2084(6), c = 14.7264(9) Å, α = 84.483(4)°, β = 77.112(4)°, γ = 87.879(3)°); 3 was found to crystallize in two forms: recrystallization from CH2Cl2 at room temperature yielded a solvent-free, triclinic phase, space group P[Formula: see text] (a = 6.5060(9), b = 7.0739(9), c = 9.1164(8) Å, α = 81.860(3)°, β = 83.406(5)°, γ = 66.589(5)°), whereas cooling a solution to –5°C yielded a solvated form, 3·CH2Cl2, which crystallizes in the monoclinic space group P21/m (a = 6.179(1), b = 10.960(2), c = 13.884(3) Å, β = 92.69(3)°). The NO2···Br intermolecular interactions observed in the unsolvated structure of 3 are disrupted in the solvate structure; the CH2Cl2 molecule in the latter is aligned such that its molecular dipole interacts with both nitro and bromo groups, retaining a molecular chain motif. The structures are discussed in relation to their semi-empirically calculated molecular electrostatic potentials and calculations of intermolecular interactions using van der Waals forces combined with an electrostatic point charge model.Key words: dithiatetrazocine, crystal structure, crystal engineering, molecular electrostatic potential.

Synthesis and reactivity of perhalogenated acyclic and metallacyclic tantalum(V) phosphoraniminato complexes: discovery of an unexpected ligand coupling reaction to form the novel phosphazenium salt

The reaction of TaCl5 with a single equivalent of Cl3P=NSiMe3 resulted in the isolation of the perhalogenated (phosphoraniminato) tantalum(V) complex TaCl4(N=PCl3) (1). Reaction of 1 with an excess of THF and subsequent cooling produced crystals of TaCl4(N=PCl3)(THF) (1.THF), which possesses a distorted octahedral Ta center with a THF molecule coordinated trans to the phosphoraniminato ligand. The reaction of 1 with the aminophosphoranimine, (Me3Si)2NPCl2=NSiMe3, resulted in a [3 + 1] cyclocondensation reaction to form the metallacyclic complex, TaCl3(N=PCl3)[N(SiMe3)PCl2N(SiMe3)] (2), which contains a TaNPN four-membered ring and a phosphoraniminato ligand (N=PCl3). The analogous [3 + 1] cyclocondensation reaction between (Me3Si)2NPCl2=NSiMe3 and TaCl5 led to the isolation of TaCl4[N(SiMe3)PCl2N(SiMe3)] (3). An attempt to cleave the NPN ligand from the Ta center in 2 via protonolysis with HCl led to an unusual phosphoraniminato ligand coupling reaction to yield the novel phosphazenium salt [N(PCl2NH2)2][TaCl6] (4). All new compounds (1.THF and complexes 1-4) were characterized by single-crystal X-ray diffraction.